Pre conditioning process for induced spawning

ABSTRACT

A process for pre-conditioning of fish in preparation for induced spawning which comprises isolating a brood stock of sexually immature or inactive fish from the natural environment by placing the stock into a water media suitable for sustaining life in a healthy condition, whereby water quality, temperature and degree of light exposure and light intensity can each be selectively controlled, adjusting the temperature and degree of light exposure and intensity so that sexual development of the brood stock is suppressed until spawning is desired and thereafter readjusting the temperature and degree of light exposure and intensity so that sexual maturity of the brood stock is rapidly attained.

United States Patent [191 Moe, Jr. et al.

[ PRE-CONDITIONING PROCESS FOR INDUCED SPAWNING [75] Inventors: MartinA. Moe, Jr., Juno Isles; Jay P.

Dunathan, Tequesta, both of Fla.

[73] Assignee: Oceanography Mariculture Industries, Inc., Riviera Beach,Fla.

[22] Filed: Nov. 29, 1971 [21] Appl. No.: 202,809

FILTER 43 er a. ULTRAVFQLET RADIATlOh 45 June 26, 1973 PrimaryExaminer-Louis G. Mancene Assistant Examiner-J. A. Oliff AttorneyNormanF. Oblon et al.

[5 7] ABSTRACT A process for pre-conditioning of fish in preparation forinduced spawning which comprises isolating a brood stock of sexuallyimmature or inactive fish from the natural environment by placing thestock into a water media suitable for sustaining life in a healthycondition, whereby water quality, temperature and degree of lightexposure and light intensity can each be selectively controlled,adjusting the temperature and degree of light exposure and intensity sothat sexual development of the blood stock is suppressed until spawningis desired and thereafter readjusting the temperature and degree oflight exposure and intensity so that sexual maturity of the brood stockis rapidly attained.

6 Claims, 2 Drawing Figures PARTICULATE 33 FILTER 37 r FVROVTEIN SKIMMER'OVERFLOW CHARCOAL AND/OR RESIN FILTER BANK PATENTEUJUIZB I975 INDUCED ICONDITIONING WNING AND FERTILIZATION I I0 v CAPTURED NATURAL STOCKINVENTORS MARTIN A. MOE,JR. J.P. DUNATHAN 5M RQLIAS IM emcchuamoIATTORNEY FILTER PARTICULATE 33 IBIOLOGICAL FILTER Fl LTER 1.1 ULTRAV LETRADIAT CHARCOAL AND/0R RESIN FILTER BANK FILTER FIG. 2

PIKE-CONDITIONING PROCESS FOR INDUCED SPAWNING BACKGROUND OF THEINVENTION l Field of the Invention:

This invention relates to a technique for preconditioning fish in orderto prepare them for induced spawning, and more particularly to atechnique whereby a fish culture can be maintained in a suitablecondition such that the spawning capability of the fish can be readilycontrolled and regulated.

2. Description of the Prior Art:

Recent increased commercial interest in the largescale cultivation, orfarming of fish, as an additional source of food supply, has generatedrenewed interest in the use of induced spawning procedures as onetechnique for stabilizing the farming output, or for controlling thetiming of maximum output to coincide with optimum marketing conditions.Although the technique of induced or artificial spawning does providesome degree of control over the extent and timing of the farming output,this control is limited to the period of from the time the fish attainspawning maturity until the period in which natural spawning begins. Agreater degree of control would be obtainable if the sexual developmentof the fish could be suppressed until spawning were desired. Under thiscondition, the fish population could be maintained for a much longerperiod of time, without spawning, so that a constant input supply couldbe available as needed for the farming operation.

Even if sexual development could be suppressed, however, it wouldadditionally be necessary to provide some technique for rapidly maturingthe fish to bring them up to spawning capacity, otherwise the gainsachieved by sexual suppression would be lost by the subsequent extendeddelay time required for normal maturation.

A need exists, therefore, for a technique in which the sexualdevelopment of a fish culture can be suppressed for an extended periodof time and thereafter brought up to full sexual maturity and spawningcapacity.

SUMMARY OF TI-IE INVENTION Accordingly, it is an object of thisinvention to provide a technique for controlling the spawning capacityof the fish culture in order to control the degree of farming output.

Another object of this invention is to provide a technique forsuppressing the sexual development of the fish culture, so that theculture can be maintained for an extended period of time withoutspawning.

A further object of this invention is to provide a technique forenhancing the sexual development of the fish culture in order that itcan be rapidly matured to full spawning capacity as required.

These and other objects have now herein been attained by the process ofisolating a stock of juvenile fish in an artificial environment in whichselective control can be attained over the water temperature, the degreeof light exposure, and the degree of light intensity.

When it is desired to suppress sexual development, a relatively coldwater temperature is maintained, depending upon the particular speciesbeing cultivated, and the extent of light exposure and intensity isminimized. The environmental conditions during this period are selectedsuch that the fish population will be maintained in an active, healthycondition, except that gonad development will be suppressed. Whenspawning is desired, the water temperature is increased and the extentof light exposure and intensity is increased so that full gonaddevelopment is rapidly attained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic of theconditioning procedure of this invention;

FIG. 2 is a schematic of one suitable brood stock maintenance systemwhich may be used in this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In discussing thisinvention, reference shall be primarily made -to the species pompano,Trachinotis carolinus, which is one of the most tasty of the salt waterfood fishes. It should be recognized, however, that pompano is referredto herein only for the purposes of illustrating the invention, and theinvention is not intended to be limited only to this particular species.In fact, this invention can be practiced with any of the large varietyof fresh water or estuarine type fishes, including: mullet, snapper,grouper, sea trout, flounder, porgies, catfish, tilapia, trout andtropical, fresh and salt water aquarium fishes.

A schematic of the conditioning procedure of this invention is shown inFIG. 1. As can be seen from the schematic, the input brood stock 1 isisolated from either natural stock 3 or by recycling a portion of theproduct from the later stages of the process 5 or partially from eachsource. The brood stock is maintained under conditions of light,temperature and fish density which are designed to suppress growth andsexual maturity, so that an input supply will be available as demandedby the process requirements. When spawning is desired, the inactive orimmature brood stock 1 is subjected to prespawn conditioning 7 in whichthe light, temperature and fish density are readjusted so that maximumgrowth and sexual development is obtained. The stock is then treated byconventional techniques to induce natural or forced spawning andfertilization 9.

BROOD STOCK MAINTENANCE In the first stage of the process, a suitablebrood stock of juvenile fish having immature or inactive sex organs isisolated, either from natural sources or from a portion of the productdeveloped in the later stages of the process, or from a combination ofboth sources, for subsequent use as an input source for the mariculture.

The isolated stock is then placed into a controlled environment which isdesigned to suppress the normal maturation and development of the fish.The purpose of this techniqueis to provide an input brood stock supplywhich can be quickly brought to full spawning maturity as supply andprocess conditions require. This technique removes the spawningprocedure from the unpredictableness of natural environmentalconditions, so that spawning can be regulated and adapted for use ineconomical fish farming operation,

If a suitable natural supply of juvenile fish is available, however, theisolation of the brood stock can be either entirely or partiallyeliminated and the natural :stock can be used directly in the subsequentprevironmental conditions, the natural source should be held inquarantine for a reasonable period of time to prevent possiblecontamination of the artificially maintained stock.

The quality and quantity of light, temperature and fish density used inthe artificial environment should be selected such that the sexualmaturation of juvenile fish will be suppressed until spawning isdesired. The particular light, temperature and fish density parameterswhich will yield the best results in terms of suppressionof gonaddevelopment will depend upon the particular species of fish being raisedFor instance, where species stimulated by decreasing photoperiods (suchas mullet) are being bred, it is desirable to provide a very long periodof light exposure, whereas when fish stimulated by increasingphotoperiods are being bred, such'as pompano, it is desirable toconsiderably reduce the extent of lightexposure.

It has been found that sexual maturation of pompano will be suppressedwhen light exposure is limited to a period of between 7 hours and llhours per 24-hour period, and most preferably between about 8% to 10%continuous hours per 24-hour period. This period is just less than the11-hour winter photoperiod of the South Florida area. The shortphotoperiod prevents the liberation of gonadotropic hormones from thepituitary gland. The intensity of light should simulate naturalconditions as closely as possible, and good results are attainable whenthe intensity is between 500 and 1,000 foot candles. This lightintensity can be obtained by the use of a high intensity fluorescentfixture in conjunction with incandescent bulbs.

If desired, natural sunlight can be used as the light source byproviding a suitable shield to limit the period of sunlight exposure.Regardless of the light source,

however, it is" essential that an interval of gradually in-' creasing ordecreasing light intensity precede each change from light period to darkperiod in order to simulate periods of 'natural dawn and dusk. It hasbeen found that sudden changes in the light intensity can cause severeshock and panic in the fish population, which can not only cause severeimmediate destruction, but can be responsible for inhibiting subsequentspawning. For the same reason, it is also desirable to provide a sourceof low intensity light, (0.01 foot candles) even during the dark period,in order to prevent disorientation of the fish, which could likewisecause severe immediate and/or long term damage.

The water temperature of the brood stock environment should berelatively low, depending upon the particular species. It has been foundthat the rate of growth and maturity of most species, including pompano,will be substantially lower in relatively colder waters than in warmerwaters under otherwise similar environmental conditions. Consequently,thewater temperature should be carefully adjusted to below the normalsummer environmental temperature for the particular species. Forinstance, where the species being bred is pompano, it is desirable tomaintain the water temperature at between l9C. and 23C.

All other environmental conditions in the controlled environment broodstock should be selected so as to simulate as closely as possible thenatural environmental conditions of the species in order that the broodstock will remain in as healthy condition as possible, suitable forfurther processing. A relatively high fish population density isacceptable in this stage.

It has been found that fish which are held under high density conditionswill mature at a much slower rate because of metabolites'and otherorganic compounds in the water. However, good water quality is alsoessential, and it is preferable to rely on environmental controls (e.g.,photoperiod and temperature) other than high population density tosuppress sexual maturation.

The brood stock may be maintained in a land-borne or sea-borne tank,vessel, or container. However, since the purpose of isolating the broodstock is to decrease or eliminate the dependency of fish growth onnatural environmental conditions, it is most desirable to provide a tanksystem which is completely removed from the natural habitat of theparticular fish species. The size of the container or vessel is notparticularly critical, except that a sufficient capacity must beprovided to assure proper aeration, recirculation, filtering and fishdensity.

Large temperature fluctuations in the water medium will have adeleterious effect on the growth and spawning capacity of the fish, andaccordingly, it is desirable that such fluctuations be carefullyregulated so that the water temperature will not vary by more than 1 or2 C. in any 24-hour period.

All other conditions in the artificial environment, other than light,temperature, and fish density, should be fairly constant and shouldcorrespond as closely as possible to the most favorable naturalconditions for the particular species being raised. The salinity of thewater, the rate of water recirculation, and the degree of filtrationshould be regulated as closely as possible to simulate naturalenvironmental conditions. When pompano is being raised, the salinity ofthe water should be maintained between 15 and parts per thousand, waterrecirculation should occur as often as times per day, and the filtrationsystem should be adequate to remove or convert ammonia nutrients andparticulate waste occurring in the environmental waters, as well assimilar impurities from the system.

If desired, a plurality of tanks or containers may be provided and thedevelopment of the brood stock may occur, either concurrently withineach container, or alternatively, the degree of brood stock developmentmay vary from container to container in order to provide a uniform inputsupply for breeding purposes.

One suitable brood stock maintenance system is shown in FIG. 2, whereina tank 21 is shown with an artificial light source 23 and a controltimer 25 for controlling the periods of relative lightness and darknessin the tank. Water 27 is pumped through a conduit 29 by means of pump 31to a particulate filter 33 which acts to remove solid impurities,food'fragments and the like. A portion of the impure water from conduit29 is subjected to a conventional protein skimmer treatment 35 for theremoval of high m'olecular weight organic substances prior to beingsubjected to the particular filter This system is further described in,and is the subject matter of, copending'application Ser. No. 66,826,filed Aug. 25, 1970 now US. Pat. No. 3,661,262.

When the species being raised is pompano, the tank waters may beexchanged up to 40 times per day and the period of light and darknessmay be obtained at a ratio of about 7 1 9 to z 17 hours per 24-hourperiod. The periods of dawn and twilight should last about 20 minutes to40 minutes, with increasing or decreasing light intensity of 100 to 10foot candles during the dusk period and about 10 to 100 foot candlesduring the dawn period.

PRE-SPAWN CONDITIONING During pre-spawn conditioning period, the broodstock is subjected to conditions which will promote rapid sexualmaturity and full development of the fish gonads, in order to preparethe fish for spawning. In order to provide this result, the stock issubjected to the opposite conditions of light, temperature and fishdensity as those which prevail during brood stock maintenance. In otherwords, where the species is a fish that spawns on increasingphotoperiod, the light duration is increased, the water temperature isincreased, and the fish density is decreased.

Where the fish species is pompano, the duration of light treatment isincreased to about 16 to 19 continuous hours per 24-hour period, usingthe same type of light source as that used during the brood stockmaintenance stage. Periods of light and darkness should continue to bepreceded by a gradually diminishing or increasing light intensity inorder to simulate twilight and dawn conditions. A source of lowintensity light should continue to be used during the dark periods inorder to prevent fish disorientation.

It is essential during this period that the temperature be maintained atbetween 25C. to 29C. as determined by the normal temperature rangesduring the spawning period in nature or slightly above, and thefluctuations in temperatures should be carefully controlled to withinabout 1 to 3C.

The degree of fish-population density is not essential. However, ofcourse, it should be below the maximum limit that the system can supportwithout distressing the fish.

The remaining environmental requirements of water salinity, aeration,filtration, and recirculation should remain substantially the same asdescribed for the brood stock maintenance. The particular pre-spawningenvironmental conditions, of course, will vary depending upon theparticular species being raised. The length of time required forpre-spawning, will depend largely upon the natural sexual developmentrate of the particular species. Where pompano is being raised, fullmaturity of the fish gonads will ordinarily occur within 6 weeks frominitiation of pre-spawn conditioning, and the exact time required can bereadily determined by periodic biopsy of samples from the fish culture.

The facilities required for pre-spawn conditioning may be substantiallysimilar to those used in the brood stock maintenance period described inFIG. 2, although since the fish density must be reduced, the size andcapacity of the holding tanks or containers may vary somewhat from thoseused during the brood stock maintenance period.

If desired, more than one tank or container may be provided so that therate of maturation will occur either As indicated above, the brood stockinput to the prespawn conditioning stage may consist of captured naturalstock and/or juvenile products from the later stages of the mariculture.

INDUCED SPAWNING Once sexual maturity of the brood stock has beenattained, as evidenced by adequate gonad development of selectedspecimens, the pre-spawn conditioning period can be terminated. Theindividual fish in the stock are then subjected to conventional hormonetreatments for the purpose of inducing spawning. As is well known,certain hormones will stimulate hormone secretions by the ovary to forceovulation. Such hormone treatments conventionally consist of either oneor two sequences of injections of a pituitary extract over a period ofseveral days. If spawning and fertilization are to proceed by voluntaryprocesses in the brood stock container, only pituitary extract of theparticular species should be used.

In an alternative approach, ovulation can be forced by injecting humanchorionic gonadotropin (HCG), to gether with a pituitary extract, intothe fish and the sperm and eggs can be physically extracted from thefish. The eggs can then be fertilized by being mixed with the sperm andtransferred to the hatching and incubation system.

Where pompano is the species being raised, two to three injections perday of from 0.5 to 1.0 cc. per kilogram weight, of pituitary extract isusually sufficient to induce natural ovulation, and from one to twoinjections per day of from 250 to 500 International units per kilogramweight, of HCG in combination with a pituitary extract is sufficient toforce ovulation.

The required aeration, filtration, circulation and environmental controlmay be the same as those used during the pre-spawn conditioning,although a much wider variation in light control, environmentaltemperature and fish density can be tolerated.

In principle, all stages of the process may be carried out in sequencein the same container or in a series of containers, although it ispreferable to use a separate container or containers for each stage. Itis most preferable, however, especially when the number of conditionedfish is large, to remove the stock from the prespawn conditioning systemin small groups to facilitate observation and treatment as inducedspawning proceeds.

Having generally described the invention, a further understanding cannow be obtained by reference to certain specific examples which arepresented herein for purposes of illustration only and are not intendedto be limiting in any manner.

EXAMPLE A brood stock of 200 pompano (Trachinotus carolinus) both maleand female types, average age 2 years, were collected in a controlledenvironment land-based tank having an inside capacityof 9,000 gallons.The fish density was 0.8 pounds of fish per cubic feet. This stock wascaptured from a wild population in the coastal waters of Florida.

A light source of eight, 40 watt fluorescent bulbs having intensity of320 watts was provided to supply 8 hours of continuous daylight typelight per 24 hours period. A low intensity light source, an incandescentbulb having an intensity of 7 b watts, was used during the period ofrelative darkness. The water environment was controlled so as to have asalinity of 30 to 35 parts per thousand, temperature of 70C. and maximumtemperature fluctuation of 2C., pH 7.7 to 8.1. Water was recirculatedthrough the filtering system at the rate of 5 times per 24 hour period.The stock was fed with 1% pounds of prepared moist food at intervals of3 times per 24 hour period. The brood stock was maintained in the systemunder these conditions for 90 days. Examination of the gonads ofselected samples from the stock showed that the full sexual maturity hadnot yet occurred at the end of this period.

The brood stock was then transferred into a second tank system having aninternal capacity of 2,000 gallons. The density in this second systemwas 0.1 pounds of fish per cubic feet. The same conditions of salinity,pH, recirculation and filtration as in the first tank were provided inthe second tank as well. The period of light exposure using a similarlight source to that as described above was increased to 15 continuoushours per 24 hour period which was preceded and succeeded by 45 minutesof gradually increasing or decreasing light intensity. During the darkperiod, a low light intensity source of'3 watts was used to preventdisorientation of the fish population. The temperature of the tank was28C. with temperature fluctuations of :LlC. The stock was fed with 8ounces of shrimp or prepared food as described above.

Full sexual maturity as determined by the development of fully maturedgonads was obtained after 10 weeks.

The brood stock was then transferredto a spawning tank; temperature 27C.i-lC.,pH 7.9, salinity 35 percent. Each specimen of the stock wasinjected once per day for 2 days with 0.5 cc. of RC0 and 0.5 cc. ofpompano pituitary extract and their eggs and sperm were physicallyremoved, mixed and placed in an egg separation tank. The live eggs wereseparated from the dead eggs using the natural buoyancy of theylivefertilized eggs and draining the bottom portion of the tank containingthedead eggs. Incubation of the eggs occurred in a tank having acapacity of 120 gallons, recirculation rate of l change/l5 minutes,water temperature 26C., 8.1 pH, salinity 35 percent, degree of aerationstrong. After 1 day, hatching of the eggs appeared to be imminent asdetermined by microscopic examination and eggs were transferred to astatic type hatching and larvae rearing tank, temperature 26C. -*.:.5C.pH, 8.1, salinity 35 percent, aeration moderate. The eggs were permittedto hatch and the larvae was retained for 25 days. The larvae were fedcultured rotifers and copepods at abundance levels of 3 to 5 organismsper cc.

At theend of'3 weeks, the fingerlings were transferred to a tank similarto that described above for prespawning conditioning in order that theycan be developed to juvenile stage. a

The conversion factor, which is defined as the pounds of fish producedper pound of food, was 2.5. That means that it require approximately 2.5pounds of food to produce 1 pound of pompano.

lt should be clearly understood that although considerable reference inthe specification has been made to pompano, it will be apparent thatmany other varieties of maritime and fresh water fish can be raised inthe same manner, simply by varying the specific environmentalparameters. Accordingly, having now fully described the invention, manychanges and modifications will be apparent to one of ordinary skill inthe art without departing from the spirit or scope of the invention.

What is claimed as new and intended to be secured by letters patent is:I

l. A process for ore-conditioning pompano in preparation for inducedspawning which comprises isolating a brood stock of sexually immaturefish from the natural environment by placing the stock into a watermedia suitable for sustaining life in a healthy condition, limiting thelight exposure to a period of between 8 and 10 continuous hours per 24hour period during which the intensity of light is between 500 and l,000foot candles and 'the water temperature is maintained between C. and23C. for suppressing the sexual development of the brood stock untilspawning is desired, and thereafter readjusting the temperature anddegree of light exposure and intensity by increasing the period of lightduration to about 16 continuous hours per 24 hour period using a lightsource having an intensity of between 500 and 1,000 foot candles and thewater temperature is maintained at between 25C. and 29C. for rapidlyattaining the sexual maturity of the brood stock.

2. The process of claim 1, wherein the fish density of the brood stockis relatively higher during the period in which sexual maturity is beingsuppressed than during the period in which sexual maturity is beingattained.

3. The process of claim 1, wherein the broodstock is isolated by beingplaced in a tank having a particulate and biological filtration systemand a recirculation system suitable for maintaining the quality of thewater sufficient for maintaining the brood stock in a healthy condition.

4. The process of claim 1, wherein each period of light exposure ispreceded and succeeded by a period of gradually increasing anddecreasing light intensity, respectively, to avoid shock or panic to thebrood stock.

5. The process of claim 4, wherein each period of light exposure ispreceded and succeeded by a period of 20 to 40 minutes of graduallyincreasing and decreasing light intensity, respectively, to avoid shockor panic to the brood stock.

6. The process of claim 1, wherein spawning of the brood stock and eggfertilization is induced by treating the stock with a suitable hormoneextract.

' n: s 1: 4r

1. A process for pre-conditioning pompano in preparation for inducedspawning which comprises isolating a brood stock of sexually immaturefish from the natural environment by placing the stock into a watermedia suitable for sustaining life in a healthy condition, limiting thelight exposure to a period of between 8 and 10 continuous hours per 24hour period during which the intensity of light is between 500 and 1,000foot candles and the water temperature is maintained between 90*C. and23*C. for suppressing the sexual development of the brood stock untilspawning is desired, and thereafter readjusting the temperature anddegree of light exposure and intensity by increasing the period of lightduration to about 16 continuous hours per 24 hour period using a lightsource having an intensity of between 500 and 1,000 foot candles and thewater temperature is maintained at between 25*C. and 29*C. for rapidlyattaining the sexual maturity of the brood stock.
 2. The process ofclaim 1, wherein the fish density of the brood stock is relativelyhigher during the period in which sexual maturity is being suppressedthan during the period in which sexual maturity is being attained. 3.The process of claim 1, wherein the brood stock is isolated by beingplaced in a tank having a particulate and biological filtration systemand a recirculation system suitable for maintaining the quality of thewater sufficient for maintaining the brood stock in a healthy condition.4. The process of claim 1, wherein each period of light exposure ispreceded and succeeded by a period of gradually increasing anddecreasing light intensity, respectively, to avoid shock or panic to thebrood stock.
 5. The process of claim 4, wherein each period of lightexposure is preceded and succeeded by a period of 20 to 40 minutes ofgradually increasing and decreasing light intensity, respectively, toavoid shock or panic to the brood stock.
 6. The process of claim 1,wherein spawning of the brood stock and egg fertilization is induced bytreating the stock with a suitable hormone extract.